Hi I was told at my clinic that the defrosting often depended on the degree of fragmentation in the cells (which they graded on a scale of 1-5). Obviously they will select the "best" embryos for the fresh transfer, and then freeze the best of the rest (or potentially if some are good, they will freeze them all anyway).
When it coms to defrosting, the embryos will have been stored in straws (usually up to 3 embryos per straw I think). So the entire straw is defrosted to see if the embryos survive (and preferably divided). Again they can put back 2. So in terms of numbers that they defrost at a time, they should only defrost sufficient straws in order to obtain 2 surviving embryos.
My embryos were quite fragmented (grades 2 and 3) and didn't survive the defrosting. However I know plenty of "frosties", and the rates seem to be improving annually - used to be about 10% success rate, but seems to be higher now.
Unfortunatly we lost all of ours (4). I was totally unprepared for that, I was on a medicated cycle and felt really confident the whole time, so was totally distraught to learn that all 4 had perished.
We then changed clinic and then thankfully had a succesful fresh cycle, the results of which is hopefully asleep next door (dd almost 3).
Then somehow, fell pregnant naturally and now have another dd (1).
However, one of my friends has a ds frostie who is the same age as my oldest daughter so it can work.
This was after our first IVF attempt in June 1999. We were very keen to give the chance of life to all of our embryos, so we froze the grade 2 and 3 embryos against the clinic's advice (it would usually only freeze grade 1 embryos). We went on to have a second cycle of IVF , where we had a Day 3 transfer (to indicate which embryos were better at multiplying),which was also unsuccessful, with no surviving embryos to freeze. I had an ovarian diathermy in April 2000 and our third IVF in June 2000 resulted in ds1 - again no survivors and the embryos transferred were of "poor quality". We had a fourth IVF attempt in Augst 2002 which resulted in ds2, and some additional embryos which were graded 4 and 5, so we decided not to freeze. IVF attempts 3 and 4 were also Day 3 transfers.
My ds is 18 months too. He was the result of our first fresh IVF/ICSI. That cycle we had no embryos suitable for freezing.
We had a subsequent fresh cycle in Jan this year which yielded 8 embryos out of 16 eggs (we have severe male factor). 7 x grade 1 and 1 x grade 2. Transferred the best 2, BFN. Then had frozen-thaw cycle, unmedicated, in May. Both embies survived the thaw and continued to divide after thawing, BFN again. So we have 4 left and we are having transfer tomorrow (yikes!) - I'm very anxious about the whole thing to be honest. I'm hoping that we get 2 out of the 4. At my clinic their average thaw rate is 70%. Mine were frozen in 2s and 1s, so if they thaw a straw of 2 and only 1 survives they then thaw a straw of 1, so none are wasted.
As to success rates, my clinic's rate is about 28% live birth rate per cycle (cf 53% for a fresh cycle). I'm having another unmedicated cycle which is a lot easier than taking loads of drugs, it makes the process much less loaded. Plus you don't need a break between cycles for the drugs to get out of your system. If this FET doesn't work we'll do a fresh cycle in Aug/Sept and push for the transfer of 3 embryos as I'll be 40 then.
All three of Lance Armstrong's children are the result of IVF. His treatment for metastatic testicular cancer rendered him infertile. Sperm samples were collected from him before he underwent treatment.